Liquid crystal display with ambient light sensor

ABSTRACT

A liquid crystal display includes a main body, a screen positioned on the main body, a backlight module positioned in the main body and supplying light for the screen, a controller for controlling the brightness of the backlight module and an ambient light sensor positioned on the main body. The ambient light sensor includes a barrel, an optical sheet positioned at an end of the barrel and a photosensitive unit positioned at the other end of the barrel. The photosensitive unit creates a signal according to the ambient light received via the optical sheet, and sends the signal to the controller. The controller adjusts the brightness of the backlight module. The optical sheet includes a first surface, a second surface opposite the first surface and a plurality of V-shaped micro structures formed on the first surface.

BACKGROUND

1. Technical Field

The present disclosure relates to liquid crystal displays and,particularly, to a liquid crystal display with ambient light sensor.

2. Description of the Related Art

There may be situations when it is desirable to use an ambient lightsensor in a liquid crystal display in an environment where there is asignificant amount of ambient light (e.g., the outdoors on a bright,sunny day). In some circumstances, a significant amount of ambient lightmay negatively affect the accuracy of an optical ambient light sensor. Atypical ambient light sensor employed in the liquid crystal displayusually includes a transparent sheet for protection. However, the lightfrom an ambient light source at a side of the ambient sensor with anincident angle greater than the critical angle may be totally reflectedat the bottom surface of the transparent sheet. That is, most of theambient light cannot be received by the ambient sensor, therebydecreasing sensitivity of the ambient sensor.

Therefore, there is room for improvement within the art.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the drawings are not necessarily drawn to scale, theemphasis instead being placed upon clearly illustrating the principlesof the present disclosure. Moreover, in the drawings, like referencenumerals designate corresponding parts throughout the views, and boththe views are schematic.

FIG. 1 is an isometric view of an embodiment of a liquid crystal displayincluding an optical sheet.

FIG. 2 is a cross-section of the liquid crystal display of FIG. 1.

FIG. 3 is a partial cross-section of the optical sheet shown in FIG. 1showing light paths.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, an embodiment of a liquid crystal display100 includes a main body 21, a screen 22, and backlight module 23, acontroller 24 and an ambient light sensor 26.

The screen 22 is positioned on the main body 21, and the backlightmodule 23 is located under the screen 22 in the main body 21. Thebacklight module 23 supplies light to the screen 22.

The ambient light sensor 26 includes an optical sheet 261, a barrel 263and a photosensitive unit 265. The optical sheet 261 includes a firstsurface 2611 (shown in FIG. 3), a second surface 2613 opposite to thefirst surface 2611, and a plurality of longitudinally parallel V-shapedmicro structures 2614 formed on the first surface 2611. The secondsurface 2613 is flat. A vertex angle of the V-shaped micro structure2614 is preferably in a range from 0 to about 90°. In the illustratedembodiment, the vertex angle of the V-shaped micro structure 2614 is45°. The barrel 263 is substantially a frustum of a cone, including afirst end portion 2631 and a second end portion 2633 with a diameterless than that of the first end portion 2631. The photosensitive unit265 is mounted at the second end portion of the barrel 263; the opticalsheet 261 is mounted at the first end portion, and the V-shaped microstructure 2614 faces away from the photosensitive unit 265.

The ambient light sensor 26 is positioned in the main body 21 adjacentto the screen 22, with at least part of the optical sheet 261 exposedout of the main body 21. The photosensitive unit 265 receives light viathe optical sheet 261, creates a signal based on brightness of theambient light, and sends the signal to the controller 24. The controller24 increases or decreases an electrical current of the backlight module23 based on the received signal to adjust the brightness of thebacklight module 23.

Referring to FIG. 3, each V-shaped micro structure 2614 includes a firstincident surface 2615 angled relative to the first surface 2611 and asecond incident surface 2616 adjacent to the first incident surface2615. The vertex angle θ is defined by the first incident surface 2615and the second incident surface 2616. Light rays α, β and γ arerefracted by the V-shaped micro structure 2614 towards a normaldirection of the first surface 2611, and the incident angle of the lightray α, β and γ at the second surface 2613 is decreased, such that theinternal reflection at the second surface 2613 is decreased. More lighttravels through optical sheet 261. The brightness of the backlightmodule 23 is adjusted by the controller 24 simultaneously.

Referring to Table 1, shown below, three test samples are provided, afirst test sample of the ambient light sensor is made using a flattransparent sheet positioned on the first end portion 2631 instead ofthe optical sheet 261. The second test sample with ambient light sensor261 with 10° vertex angle of V-shaped micro structure 2614. The thirdtest sample with ambient light sensor 261 with 20° vertex angle ofV-shaped micro structure 2614. Emitted light of predetermined incidentangle travels through the three test samples, with the brightness(lumen) detected by the photosensitive unit 265 is also provided in eachsheet of Table 1.

TABLE 1 Incident The first test The second The third angle sample testsample test sample 10 184.96 212.63 213.52 20 103.57 146.87 162.79 3047.69 66.25 99.67 40 17.22 23.91 41.18 50 7.53 13.36 18.27 60 3.44 7.328.86 70 1.15 3.55 4.59 80 0.11 1.26 2.25Table 1 shows that the second and the third test samples with opticalsheet 261 receive more light than the first sample. The photosensitiveunit 265 of the third test sample with optical sheet 261 having vertexangle θ exceeding that of the second test sample receives more lightthan the third test sample. That is, as angle θ increases, more lightpassing through the optical sheet 261.

Finally, while particular embodiments have been described, thedescription is illustrative and is not to be construed as limiting. Forexample, various modifications can be made to the embodiments by thoseof ordinary skill in the art without departing from the true spirit andscope of the invention as defined by the appended claims.

1. A liquid crystal display comprising: a main body; a screen positionedon the main body; a backlight module positioned in the main body andsupplying light to the screen; a controller for controlling brightnessof the backlight module; and an ambient light sensor positioned on themain body and comprising a barrel, an optical sheet positioned at an endof the barrel and a photosensitive unit positioned at the other end ofthe barrel, the optical sheet comprising a first surface away from thephotosensitive unit, a second surface opposite to the first surface anda plurality of V-shaped micro structures formed on the first surface;wherein the photosensitive unit creates a signal according to theambient light received via the optical sheet, and sends the signal tothe controller, then the controller adjusts the brightness of thebacklight module.
 2. The liquid crystal display of claim 1, wherein theV-shaped micro structure comprises a first incident surface angledrelative to the first surface and a second incident surfaceperpendicular to the first surface.
 3. The liquid crystal display ofclaim 1, wherein a vertex angle of the V-shaped micro structure is in arange from 0 to 90°.
 4. The liquid crystal display of claim 1, whereinthe vertex angle of the V-shaped micro structure is 45°.
 5. An ambientlight sensor comprising: a barrel; an optical sheet positioned at an endof the barrel; and a photosensitive unit positioned at the other end ofthe barrel, wherein the optical sheet comprises a first surface awayfrom the photosensitive unit, a second surface opposite the firstsurface, and a plurality of V-shaped micro structures formed on thefirst surface.
 6. The ambient light sensor of claim 5, wherein theV-shaped micro structure comprises a first incident surface angledrelative to the first surface and a second incident surfaceperpendicular to the first surface.
 7. The ambient light sensor of claim5, wherein a vertex angle of the V-shaped micro structure is in a rangefrom 0 to 90°.
 8. The ambient light sensor of claim 5, wherein thevertex angle of the V-shaped micro structure is 45°.